This paper discusses the rationale and developmental issues for a sideview presentation vertical situation display (VSD) for use in commercial transport airplanes. The rationale for the VSD stems from the apparent need in the commercial aviation environment for better vertical situation awareness than that seen in the flight deck of today. Vertical situation information such as altitude, selected altitude, radar altitude, flightpath angle, and desired flightpath are currently dispersed throughout the flight deck, imposing high cognitive demands on the pilot. The integration of all relevant vertical situation information into a single pictorial format should facilitate the pilot's assimilation, understanding, and use of the required information.Use of a sideview presentation of the flight situation would allow altitude related information used for both the primary flight task and vertical navigation to be combined. This allows the pilot to compare the current vertical situation with future requirements. A pictorial combination of control, performance, and navigation information should aid the pilot in quickly and easily developing a complete mental picture of the vertical situation. During time-critical or high workload situations, this capability could prove invaluable in assessing the situation.Development will progress in an iterative manner with the current emphasis on type of usage, type of situational presentation, and actual informational needs being evaluated in a flight simulator. Once the baseline format is established, a series of studies will be conducted to identify and optimize those display variables found to be critical for performance. It is believed that the inclusion of a VSD into the flight deck would increase vertical situation awareness, while reducing pilot workload, and the potential for pilot error.